Abstract

We have used density functional theory calculations to study the adsorption of hydrazine on a number of low-index copper surfaces, which are found in the experimentally produced shapes and structures of copper nanoparticles. The (111), (100), and (110) surfaces have been modeled as slabs, and we have measured their interaction with the experimental reducing agent hydrazine, N2H4, which strongly favors the gauche conformation. Our calculations show that hydrazine binds most strongly to the (110) surface, where the hydrazine bridges surface copper atoms with the molecule twisted to avoid an eclipsed structure. However, similar bridging structures are found to be unfavorable on the (100) and (111) surfaces. Oil these surfaces, one of the nitrogen atoms favors the atop site of a surface copper atom and the molecule is inclined to the surface, retaining the gauche configuration. Various low-energy structures on each surface have been compared, and for the most favorable adsorbate/surface configurations, the strength of binding of the molecule shows the order (111) < (100) < (110). The change in experimental crystal shape found with increased hydrazine concentration in the reaction mixture may be explained by the stronger binding of hydrazine to the (100) faces compared to binding to the (111) faces, which results in growth on the (111) faces: pentagonal particles grow to elongated particles, spheres grow to cubes, and the triangular particles observed are composed entirely of (111) surfaces.

Type:

Article

Title:

Density Functional Theory Calculations of the Interaction of Hydrazine with Low-Index Copper Surfaces